Compositions for use as protective layers and other components in electrochemical cells

Abstract

Electrode structures and electrochemical cells, including lithium-sulfur electrochemical cells, are provided. The electrode structures and/or electrochemical cells described herein may include one or more protective layers comprising a polymer layer and/or a gel polymer electrolyte layer. Methods for making electrode structures including such components are also provided.

What is claimed is: 
     
         1 . A lithium-sulfur electrochemical cell, comprising:
 an anode comprising lithium metal or a lithium metal alloy;   a polymer layer comprising a polymeric material, wherein the polymeric material comprises a branched polyimide formed by reaction of:   (a) at least one polyimide selected from condensation products of:
 (α) at least one polyisocyanate having on average at least two isocyanate groups per molecule; and 
 (β) at least one polycarboxylic acid having at least 3 COOH groups per molecule or an anhydride or ester thereof; and 
   (b) at least one diol or triol; and   a cathode comprising sulfur.   
     
     
         2 . A lithium-sulfur electrochemical cell, comprising:
 an anode comprising lithium metal or a lithium metal alloy;   a polymer layer comprising a polymeric material, wherein the polymer material has a decomposition temperature of greater than or equal to about 200° C.; and   a cathode comprising sulfur,   wherein the electrochemical cell is adapted and arranged to operate at a temperature of greater than or equal to about 150° C. without employing an auxiliary cooling mechanism and without the electrochemical cell experiencing thermal runaway.   
     
     
         3 . The electrochemical cell of  claim 1 , wherein the polymer layer is formed from at least one reaction product of:
 (a) at least one polyimide selected from condensation products of:
 (α) at least one polyisocyanate having on average at least two isocyanate groups per molecule; and 
 (β) at least one polycarboxylic acid having at least 3 COOH groups per molecule or an anhydride or ester thereof, and 
   (b) at least one diol or triol,   said reaction product being subsequently reacted with   (c) at least one polyisocyanate having on average at least two isocyanate groups per molecule.   
     
     
         4 . The electrochemical cell of  claim 1 , wherein the at least one polyisocyanate (α) has on average at least 2.5 isocyanate groups per molecule. 
     
     
         5 . The electrochemical cell of  claim 1 , wherein the at least one polycarboxylic acid (β) has on average 4 COOH groups per molecule or an anhydride or ester thereof. 
     
     
         6 . The electrochemical cell of  claim 1 , wherein the at least one polycarboxylic acid (β) comprises an anhydride group. 
     
     
         7 . The electrochemical cell of  claim 3 , wherein the at least one polyisocyanate (c) has on average 2 isocyanate groups per molecule. 
     
     
         8 . The electrochemical cell of  claim 3 , wherein the at least one polyisocyanate (c) has on average at least 2.2 isocyanate groups per molecule. 
     
     
         9 . The electrochemical cell of  claim 3 , wherein the at least one polyisocyanate (c) has on average between at least 2 and up to about 6 isocyanate groups per molecule. 
     
     
         10 . The electrochemical cell of  claim 1 , wherein the polymer layer is incorporated into a separator positioned between the anode and the cathode. 
     
     
         11 . The electrochemical cell of  claim 1 , wherein polyisocyanate (α) is selected from oligomeric hexamethylene diisocyanate, oligomeric tetramethylene diisocyanate, oligomeric isophorone diisocyanate, oligomeric diphenylmethane diisocyanate, oligomeric toluylene diisocyanate and mixtures of the above mentioned polyisocyanates. 
     
     
         12 . The electrochemical cell of  claim 1 , wherein polymer layer has a thickness in the range of from about 1 to about 20 μm. 
     
     
         13 . The electrochemical cell of  claim 1 , wherein the polymer layer has a thickness in the range of from about 1 to about 10 μm. 
     
     
         14 . The electrochemical cell of  claim 1 , wherein the polymer layer has a thickness about 1 μm. 
     
     
         15 . The electrochemical cell of  claim 1 , wherein polyimide (a) has a polydispersity M w /M n  of at least 1.4. 
     
     
         16 . The electrochemical cell of  claim 1 , wherein the polyimide (a) has a polydispersity M w /M n  of between about 2 and about 4. 
     
     
         17 . The electrochemical cell of  claim 1 , wherein the polymer layer is directly adjacent the anode. 
     
     
         18 . The electrochemical cell of  claim 1 , wherein the polymer layer is directly adjacent the cathode. 
     
     
         19 . The electrochemical cell of  claim 1 , wherein the polymer layer functions as a protective layer for the cathode. 
     
     
         20 . The electrochemical cell of  claim 1 , wherein the polymer layer functions as a protective layer for the anode. 
     
     
         21 . The electrochemical cell of  claim 1 , wherein the cathode includes elemental sulfur as a cathode active species. 
     
     
         22 . The electrochemical cell of  claim 1 , wherein the polymer layer comprises at least one lithium salt. 
     
     
         23 . The electrochemical cell of  claim 22 , wherein the lithium salt is selected from LiNO 3 , LiPF 6 , LiBF 4 , LiClO 4 , LiAsF 6 , Li 2 SiF 6 , LiSbF 6 , LiAlCl 4 , lithium bis-oxalatoborate, LiCF 3 SO 3 , LiN(SO 2 F) 2 , LiC(C n F 2n+1 SO 2 ) 3 , wherein n is an integer in the range of from 1 to 20, and salts of the general formula (C n F 2n+1 SO 2 ) m XLi with n being an integer in the range of from 1 to 20, m being 1 when X is selected from oxygen or sulfur, m being 2 when X is selected from nitrogen or phosphorus, and m being 3 when X is selected from carbon or silicon. 
     
     
         24 . The electrochemical cell of  claim 1 , wherein the ionic conductivity of the polymer layer is at least about 1×10 −4  S/cm at room temperature in a swollen state. 
     
     
         25 . The electrochemical cell of  claim 1 , wherein the polymer layer is stable to an applied pressure of at least 10 kg/cm 2  in a swollen state. 
     
     
         26 . The electrochemical cell of  claim 1 , wherein the polymer layer is a gel polymer layer. 
     
     
         27 . The electrochemical cell of  claim 1 , wherein the electrochemical cell comprises the solvents 1,2-dimethoxyethane and/or 1,3-dioxolane. 
     
     
         28 . The electrochemical cell of  claim 1 , wherein diol (b) is a polyalkyleneoxide. 
     
     
         29 . The electrochemical cell of  claim 1 , wherein diol (b) is polyethylene oxide, polypropylene oxide, polybutylene oxide, or polytetrahydrofuran (poly-THF). 
     
     
         30 . The electrochemical cell of  claim 1 , wherein the branched polyimide has a decomposition temperature of greater than or equal to about 200° C. 
     
     
         31 . The electrochemical cell of  claim 1 , wherein the electrochemical cell is constructed and arranged to operate at a temperature of greater than or equal to about 150° C. without employing an auxiliary cooling mechanism and without the electrochemical cell experiencing thermal runaway.